The present invention relates to a speed adjusting device for a drill wherein the output shaft is connected to a first pulley which is connected with a second pulley by a belt. Each pulley is composed of two disks which are respectively retained by two respective retaining means. The two disks can be separated from or moved toward each other to change an effective radius of the belt so as to adjust a speed of the output speed.
A conventional power transmission system for a drill is shown in FIG. 1 and generally includes a motor 10 having a shaft 11 which extends into a box and is securely connected to a first set of gears 12 which includes a plurality of grooves with different diameters. A second set of gears 13 is located in the box and has a plurality of grooves with different diameters. The second set of gears 13 is connected to an output shaft 14 and a drill clamping device 140 is connected to the output shaft 14 so that a drill bit is connected to the drill clamping device 140. A belt 15 is engaged with the two respective grooves in the two set of gears so that when the motor 10 is actuated, the second set of gears 13 is rotated by the belt 15 so as to let the drill bit drill into an object. In such a power transmission, the output shaft 14 can only rotate at a fixed speed because the position of the belt 15 is secured. When the speed of the output shaft 14 needs to be changed such as when the object to be drilled is different, the users have to stop the motor 10 completely and then removes the belt 15 from one groove to another so as to obtain a different effective diameter on the gears to change the rotational speed of the output shaft. It takes time and break the consistency of working.
The present invention intends to provide a speed adjusting device for a drill and the speed can be easily changed without stopping the motor and simply by rotating a wheel on outside of the drill.
In accordance with one aspect of the present invention, there is provided a speed adjusting device for a drill and comprising a first pulley assembly movably mounted to a motor shaft and the first pulley assembly comprising a first fixed disk and a first movable disk. The first fixed disk is fixedly connected to the motor shaft and the first movable disk is movably mounted to the motor shaft. Each of the first fixed disk and the first movable disk has an inclined surface facing each other. A spring is biased between the first movable disk and the motor. A second pulley assembly comprises a second fixed disk and a second movable disk. The second fixed disk is fixedly mounted to a driving shaft and the second movable disk is movably mounted to the driving shaft. Each of second fixed disk and the second movable disk has an inclined surface facing each other. An output shaft is connected to the driving shaft. A belt is movably engaged between the first fixed disk and the first movable disk, and between the second fixed disk and the second movable disk. A pressing member has a first pivotally connected a frame and a second end of the pressing member presses on the second movable disk. A lifting means is connected to the pressing member.
The object of the present invention is to provide a speed adjusting device for a drill wherein the motor is running while changing the speed of the output shaft.
Another object of the present invention is to provide a speed adjusting device for a drill wherein the speed can be changed by rotating a wheel.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.